Your phone is NOT killing you

today I want to write about ionizing and non-ionizing radiation and also mobile phones as serial killers.

When somebody says radiation they mean electromagnetic radiation. Light is of course an electromagnetic radiation but only small part that we can see.

Visible light makes only very small part of whole spectrum.

The energy of light is connected with its frequence, as it rises (to left) energy increases as well. Gamma rays are the most energetic part of spectrum, they appear in radioactive decay and the are also created in Sun. Radiowaves on the other hand have enormous wavelength and very small energies, this is very good because it means that they are easy to create and also not harmful to human.

When we talk about radiation we can say that it is either ionizing or non-ionizing. If it is ionizing it means that it can create ions. Ions are either positively or negatively charged atoms, ions are created when they get or lose an electron which happens when photon hits the electron, but not always. If the energy of the photon is high enough then it will happen (ionizing) but if it is not the nothing will happen (non-ionizing).

How does this corresponds to your phone?

Well there have been some studies that showed that frequent phone users had higher chance of getting brain tumor. This would be caused by the photons that are transmitted from your phone. They should apparently hit DNA and other stuff in your cells and by ionizing these atoms, make change and possibly develop cancer.[0]

The radiation that is used in your phone is with the wavelength of tens of centimeters which means something like low radiowaves. Photons in this part of spectrum would not be able to knock electrons from atoms at all [1].

While for example study from Sweden showed that brain tumors and phone usage correlates, the study was not so well made. The problem is that you need gigantic sample since brain tumors are very rare (3/100,000 people). In short, the best thing you can do is to look on the number of brain tumors before “everyone” started to use cell phone and compare it to the number brain tumors right now…


There is no correlation whatsoever!


If you want more detail about the studies and so on, check out these two videos:

[0] I was just thinking that if radiowaves cause cancer than we should probably be much more conserned about ultra violet that is roughly million times stronger!

[1] Einstein got Nobel prize for finding the photoelectric effect which is basicly the knocking of electrons by photons. He found out that under certain frequency the atoms will not be ionized because the energy is not high enough (this critical point is different of course for different elements).




Optics: 7) So is it wave?

in last post I was talking about the experiment that proved that light is wave, it is creating interference in the double slit experiment instead of two lines which one would assume if it was behaving as a particle. (You can imagine bullets instead of particles).


If light was behaving as particle

So I found out that the particle part of light is bit more complicated so I wont try to explain it so much in the PRO sense but rather in few words, if you are more interested check out this page: 1)

With this theory that light is just a wave there were finally find some problems.

If you would very accurately measure light on some spot and this light would be dimmer and dimmer, you should get dimmer and dimmer picture. But at one point there were just dots!


As the light is getting dimmer, with very good camera you can see that some pixels get much more energy than other.

As you might understand this was quite confusing. Wave should not make pattern like this.

Soon it was found out that when you measure brightness you can find bumps that should not be there if light would be wave, rather it should be quite uniform.

Finally what was concluded from this is that light behaves both as wave and particle, the attribute is called particle-wave duality.

What was also found at this time (something like beginning of 20th century) is that light comes in quantas. This has very interesting effect. If you would walk away from candle and would be able to distinquish individual photons at one point the candle would not shine less and less because at one point there will be only one quantum coming to you and quantum is not divisible so it would start to disappear more and more often but it would always shine. More detail here:

It was also found that not only photon but also other subatomical particles behave like waves and particles. In 20th century it was tested with electrons and sure! They also made this interference pattern on detector.


PS: This is my 200th post!






Optics: 6) Experiment that changed our thinking

today I will again write about optics but I have to return at the very beginning of 19th century when Thomas Young proved that light is behaving like a wave.

So there was this problem.

Newton thought that light has to be lot of particles, he called them corpuscles.

At the same time Huygens thought that light is behaving like a wave.

Then came this smart guy called Young. He conducted easy experiment to prove this.

The experiment is based on phenomena called interference of light. Imagine two people calling. When they both call at the same time. The called person is more likely to hear the call because they amplify the sound together. Now imagine that they want the person to hear some word that they are repeating again and again, such a word could be: RETURN!

When they call both at the same time it will make mega RETURN! And you can be sure that the person will hear it. But if one of them is slower by just a fraction of the time that it takes to say the word, whole message is destroyed:

1st person:   |return!|
2nd person: |return!|
1st person:   |return!|
–> retuRneturn
2nd person:         |return!|
From the second example you can clearly see that if it is just a little windy the message may end up some thing like: “ertueruterut” and that is something you do not want. So light behaves in the same way. If both lasers are calling “red” at the same time you will get mega red (amplyfied red, with higher amplitude). If not well, you know what happens!

But analogies can take as only so far. There is one more problem. In my example if one person would call: “return” and the other “go away” the message should be destroyed. But with light, nothing happens, the words (colors) do not interact at all (in this way) because to interact the frequency has to be the same, this is called coherence of light.

So how did he use the interference of light to prove that light behaves like a wave? In his experiment imagine having a dark room with one small hole that leads to another two holes like this:

As the light passes through both slits it creates interesting pattern that is unique for waves.

If light would be particle you would see two lines on the right. But instead what happened was that at some places the amplitude was increased, as both sources (both slits) were calling (shining) at the same time or they were just moved by one word (one top of wave).[1] So some of the light is in consctructive interference (peaks on the black line) and some parts of the wave is in destructive (bottoms of the black line). This creates lighter parts and darker parts:

The double-slit experiment

And finally animation:

The light passing through both slits, green part is destructive, blue, red and yellow constructive.


If you are not still sure about this, watch the video below:

[1]By this I mean that one person starts calling: “return return return” and the second joins for the second return so they are moved by one period.




Why do we use CMYK instead of RGB? (Very colorful post)

maybe you too wondered why there is written CMYK on printers. If you have printer or you found out what it means you too know that it is abbreviation for: Cyan, Magenta, Yellow (and K which I will tell later).

What CMY stands for?



Those are the colors that you have to fill inside the machine to print you stuff. Sure this is ok, but why do not we use RGB (red, green, blue)? It seems to be used everywhere so why not in printers?

I thought this because I was thinking that from RGB you can get any color, and sure you can, but only in additive process. Such a process happens for example with light, white light is made up of many different parts with different wavelengths that ADD up. So what does mean that something is red(?), well it reflects only red light absorbing the rest. If you put there blue the material will be even more darker because it will reflect only the combination of blue and red. If you combine everything it would not reflect at all, the object would be black.

This is an example of substractive process with colors. You can see that RGB is darker since you will get it by substracting CMY.

So what you want to do is to start with lighter colors, those are cyan, magenta and yellow. They too are able to add up to all other colors + lighter than RGB in this subtractive form. Even then colors are not perfect in printers so you can not add up to some, bright red, blue  and green wont be displayed very well.







What the “K” stands for? It stands for “Key” which is the color black (it is the KEY thing). While CMY can add up to black, it would not be very pure since the colors can not be clean, it was decided that there will be black added because in most texts black is used. The letter “K” was used because “B” was already used in the RGB model.


PS: check out these two links about colors shared by Jim Ruebush, they are truly amazing:
1) 2)


How does optical fiber work?

so again, as I was studying some optics I found something that interested me. This time it was optical fiber which is the cable that may be running under your way to work bringing you some interner connection.

Optical fibers are cables that are carrying signal. They are made of two pieces of glass with different indexes of refraction. When electromagnetic radiation (light) travels through this tunnel that is made by this cable it bounces off the sides if it is in big enough angle.

There is value called critical angle in which light will always bounce on the edge of two mediums. It depends on refractive index.

This kind of communication is very useful one because glass is very cheap compared to some metals and the communication can not be destroyed by some magnetization. Also

The optical fibre has to be protected in some material, the core itself may be in micrometers.

Optical fibres are usually packed in nice groups.






those tubes made up of glass are quite flexible.


By transmitting signal on one side usind some diode you can few kilometers away decode this signal based for example on the number of pauses and number of incoming light waves. Such a communication may reach amazing speeds of tens of gigabytes per second.

There are two main types of optical fibers. First one are multi-mode fibers.Those are the ones for a shorter distance, roughly 600-1,000 meters. There is lot of light running there and it is used to deliver signal in buildings. If you would use it for longer distance the light would stop traveling predictably.

The second type is single-mode fiber. This is much thinner and works on the distance of tens of kilometers. It is used between countries and cities.





Cycling faster than light

so while I was learning some optics, I bumped into this page that talked about refractive index which I was just studying. I wondered what is the highest refractive index ever found and there it was, not in number though I think we can calculate it.

Refractive index

Since you probably have not read my post about refractive index or you have not heard about it, it is dimensionless value that shows how much is light (electromagnetic radiation) slow in the medium where it travels and also how much it will change its direction when traveling through one medium into the other. You can calculate the index like this:


Where n is the refractive index, c is speed of light in vacuum and v is the velocity in the medium you are talking about. From this, it is easy to see that vacuum and only vacuum has the refractive index exactly 1 because there is nothing that blocks its way and you just divide speed of light in vacuum by speed of light in vacuum.

So as the index of refraction increases the only thing that can change is velocity in the medium and it is decreasing.

I found that scientists were able to create stuff in which the light was traveling in “only” 17 meters per second! This is 61.2 kilometers per hour. From steep hill or if you are really good cyclist you can be faster than that, though I think it is bit more easier and safer to do it in car.

So what is the refractive index of this miraclous stuff? Roughly 17,647,059. While normally n lies somewhere between 1 to 3.

What is this thing made of? 

… gas of sodium atoms – a high-tech version of the insides of the bulbs of street lamps – cooled to within a fraction of a degree above absolute zero … the effect of cooling reduces thermal effects, and this in itself contributes to the retardation of light.

There is also special state of matter created that packs those atoms closer together.



Optics: 5) Magnifier and microscope

today I will finally continue to write about optics. Last time I was talking about dioptre and today I will explain how magnifier and microscope works.

Angle of view

Angle of view plays important part in magnifier, microscope and so on. The problem why we can not see individual cells in leaf with naked eye is that we are not able to distinquish things that are too close to each other. Human eye is able to distinquish things that are about 1′ (arc minute=1/60° degrees) apart.

You can easily try it when you draw something on paper and then walk away from it. Or you are not able to tell trees apart when you are hundreds meters away from them.

(On the picture you can see the angle of view for camera, it can be measure horizontaly, verticaly or diagonally).

To make this angle bigger so we can distinquish everything we can walk towards stuff. But when we have a leaf we can get only limitely close to its surface and our eye can not adjust to something so close. Look at your thumb when you put it three centimeters from your nose. It will be blurry even if you try your best, this is because your eye does not have enough dioptre to make the image clear, plus your eye is going to hurt because of the muscles in eye stretching to make the optical power of your eye bigger. Conventional visual distance is distance for which human eye has to release least effort, this is about 25 centimeters.

To know the distance two objects must be apart to distinquish them we can use tangens:

tg τ=y/d

τ is the angle of view which is for human 1′.
y is the distance of two objects which you are trying to distinquish.
d is the distance from you to the objects.

y=d * tg τ

So the limit of our eye is that it is not able to be powerful enough so we need something which will help us and it has to work the same way as our eye, magnifier!

The light rays are going too much away from each other and your eye is not able to change their direction to create picture.


There is thing called angular magnification.

γ=τ’/τ = tg τ’/tg τ =  y/f/y/d = d/f

γ is the angular magnification and is the distance to focal point.

Angular magnification says to us how much our magnifier is strong. The formula above works for objects that are right in focal point, otherwise there would be “a” which is the distance to the object. If the object is right in focal point our eye does not need anything to do and as it gets closer the light rays are more and more going apart so that at one point you will need better magnifier and then it just wont be enough so you will have to use microscope.


There are two lenses in microscope. The first one is close to the object and it has the largest dioptre possible, making its focal point small as possible. It is called objective lens.

The second one is not so strong and its role is to make finally adjustment of light rays so they create image in your eye.

Optics 5, Pic 1

The picture above which I drew is horrible wrong but I can describe what is going on there. On the right you have the small object (brown). There is light coming from it in all various angle but important is that the lens has enough dioptres to use them all. F’ is the focal point of second lens, this point should be at the distance where all the rays from first lens converge into one point but I was not able to draw it properly. This is the way microscope is designed. Those rays start to go apart again but soon they hit the second lens, converging again and entering the eye in proper angles so that they hit all the spots on red line creating much bigger image.

Microscope is not unlimited source of magnification since when you will try to make bigger something too small you will get into problem with the wavelength of light.


Optics: 4) Measuring dioptre

today I was doing the best thing in optics to date. I was measuring the dioptre of my glasses (yes I wear glasses) and also I measured the dioptre of my magnifier (yes I measured it but then I figured out that I did it wrong so I will skip it).

Ok, before I get to the measuring and how I did it I will explain how lenses work because in last episodes what I did were only mirrors.

The difference between mirrors and lenses is that mirror reflect light while lenses let it through while changing its direction of travel.

There are several types of lenses which can be sorted to two main groups Pic1, Optics 4of convex lens and concave lens.

On the huge picture you can see the six types. The first row are convex lenses. First one is called biconvex lens then planoconvex lens and the third is concave-convex lens. You can see than there is always convex which hints for the first row, for convex type.

It is similar with the second type, those are biconcave lens, planoconcave lens and convex-concave lens.

I know this is cool, what can we do with this?
This equation which you can see on the left is the equation for lens which is thin. This means that there is no space between the arcs of the lens by this I mean that the arcs touch . Those arcs you can see on the right of the first picture. r1 is radius of the first arc and r2 of the second. f is the focal distance, the distance from focal point to the middle of the lens. The thing here is that lens has two focal distances, that is because it is made of two parts separeted by the vertical axis as you can see on the next picture. Also this whole equation not only equals to 1/f but also to φ(phi). The unit of φ is dioptre so φ=1/f. If f increases dioptre decreases logicly. So if someone has glasses with 4 dioptre his focal distance is 25 centimeters because dioptre is measured in meters!
This equation can be used both for concave and convex lenses of course (but concave lens will have r negative).

n1 and n2 are the refractive index of the glass which is around 1.6 and of the stuff where the lens is in, air, water or something else (n2 is the higher one).

You can find lot of problems on this equation and I did some from one book. It is good to exercise some of them because then you will feel much better on the stuff you are actually doing.

Now last thing before I get to the glasses, lets see how convex lens react to the three main rays which I mentioned in earlier postsPic2, Optics 4 (I will do the concave lens next time because I did not get to it yet).
When the candle is in about twice the distance of the focal point you can see that the size is fairly similar and what concave lens does, is that those light rays which are going from each other will be headed back towards the same point where the image will be formed. Of course the problem is that you wont see the picture of something when you put your lens from your glasses on the paper. It is because there is whole other bunch of rays from all different sides that will disturb any image that could be made.

Pic3, Optics 4When you look on the picture above, you can see that blue and green line were not able to touch anywhere which is the same thing that happened with the mirror when you put something between the mirror and focal point.

This image is enlarged and not true image since the rays are not actually going that way but our eye thinks so.

I was measuring the dioptres of my glasses. For the right eye I have -2 dioptres. You see it is very important that it is minus because that is what is saying that it is concave lens.
I took the glasses and drew line on the paper of their bottom side, which I then expanded and tried as accurately as possible to find out the radius of this circle 9.2 for the inside of concave lens and 12.8 for the outer part.

Do not forget that those glasses are concave convex lens which also means that the inside is -9.2 because it is “negative” of the glass.

When I gave it to the equation I found out that focal distance was 54.52 centimeters and dioptres -1.8342 which is not very close but since the way I was doing this was not meant to be very accurate I could not get anything better. (I took the refractive index of glass to be 1.6).


PS. this was my 100th post!
PPS. I will update about those glasses because I am not totally sure yet how they work so stay tuned.
Picture of equation
Picture of magnifier


Optics 2) Snell`s law

here it comes, here it goes! This is gonna be probably my first post where some real physics is involved (actually it is far too easy)! I am going to write about Snell`s law which is the law describing how light changes the angle of traveling when it enters to different medium.

First of all I have an experiment for you which goes as follows: you take a bowl which for the start will be empty except some small thing that will sink in water later on.
1) place your chin on the edge of table and move the bowl so you can see what is inside.

2) move it on the place where the edge will block your view and then place a water inside.

3) You should see the thing inside again!
This is because the light changes its angle of traveling which makes for example straw in bottle of water look so distorted (or hunter`s eye cheated when he is seeing the fish on different place then where it actually is (this makes water not look so deep as it actually is)), as that the higher part is not even connected sometimes to the lower one.
On the picture on the left you can see that the lower and upper part does not match which is because of the light which change the angle of traveling when entering glass then water then glass and air.

Fine, so what depends on how much will the angle change?
It is the difference between the speeds of light in both medium.

There is thing which is called refractive index: n. All mediums (which do let some light through) have some refractive index. Vacuum has 1, it does not change the angle of light. Air has about 1,0003 so you will usually see 1 also. But water has 1.33 and refractive index of glass ranges from 1.5 to 1.9 and the highest index known is for germanium=4.

When light enters another medium Snells law comes!

\frac{\sin\alpha_1}{\sin\alpha_2} = \frac{v_1}{v_2} = \frac{n_2}{n_1}
Btw. if you want to know n.. n=c/v (c is speed of light and v is the speed of light in current medium)

On the left you can see the example of light ray traveling from one thing to another. So for example if you did not know the angle in which it will fly in the second medium (water now) you would do this:

sin 50°/sin beta=1.33/1
sin 50°/1.33=sin beta
0.77/1.33=sin beta
0.58=sin beta
This is all beta about which I am talking here would represent theta two on the picture. So if you have enough information you can either get the angles or the speeds of light in mediums or the refractive indexes.

On the gif you can see pretty neat animation of how the waves of light are slower in the water and the red line clearly represents how the light is refracted.


Pictures except the first one are from wikipedia pages about refractive index and Snell`s law.
If you want to check out my first post about optics click here.
1st picture source


Optics: 1) Reflection

here it comes, here it goes. I realized that if I want to really know something about astronomy I have to use physics. For now my first goal is to learn something about optics and particularly about binoculars and how they work and what is the math involved! Today I will write about very basics and it is reflection of light. Probably I will add something to it on my YouTube channel with some examples and I bet it will be fun!

When we are talking about optics and stuff around we assume that light or electromagnetic radiation behaves as particle (on the level where I am), the thing is that as rest of the really small particles like quarks and electrons and neutrinos, light behaves both as particle and wave which called wave-particle duality. This is very interesting but let it be for now.

As you see on the first picture from wikipedia article reflection, there is laser pointed on mirror which as you can see is reflected to the right.
This is important, the light gets reflected from mirror because photons bounce in the same angle from which the came.
On the right you can see the ray of light starting at P, reflecting from O and flying to Q. Both of the angles are are same from imaginative line that has 90° angle with the mirror. θr=θi  … r stands for reflected and i stands for incident. This also means that the angle of the ray and the mirror equals to the one on the other side. This is for mirror but of course other things are reflecting light too but because their surface is not smooth photons are flying all around and you want get the exact image of the thing that was emitting/reflecting the light first even if it is not absorbing any spectrum like snow. This is also the reason why it is dangerous to not wear anything across your eyes when you are a long time on place where is snow because over time all of this light can blind you.

This can happen in matter of couple of seconds if you look directly into Sun since the inside of the eye can be sun-burned in similar way like your skin and the damage may be permanent so watch out!